1 Answer

By "now won't start" I'm assuming you mean the engine won't turn over.

The battery might be good but it sounds like the alternator might be bad and was not charging the battery as you were driving. Check to make sure the belt is OK. A worn belt can slip and not operate the alternator correctly. Also check the cables on the battery. Make sure both the positive and negative battery cables are tight. A bad connection from either one can cause the battery to not charge properly. See if anyone is around who can jump start the vehicle for you. If jump starting it works and the vehicle starts, then I would have the alternator tested.  

Or it could be as simple as, you are out of gas.